1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus to which a process cartridge is detachably mountable for forming an image on a recording medium, and a process cartridge push-in mechanism for pushing the process cartridge into a main body of the image forming apparatus in mounting the process cartridge to the main body of the image forming apparatus.
The term "electrophotographic image forming apparatus" refers to an apparatus for forming an image on a recording medium by an electrophotographic image forming process. Examples of such image forming apparatus include an electrophotographic copying apparatus, an electrophotographic printer (for example, a laser beam printer and an LED printer), a facsimile apparatus and a word processor and the like.
Also the term "process cartridge" refers to a cartridge integrally containing charging means, developing means or cleaning means and an electrophotographic photosensitive drum, and rendered detachably mountable on the main body of the electrophotographic image forming apparatus. It also refers to a cartridge integrally containing at least one of the charging means, developing means and cleaning means, and an electrophotographic photosensitive drum and rendered detachably mountable on the main body of the electrophotographic image forming apparatus. It further refers to a cartridge integrally containing at least developing means and an electrophotographic photosensitive drum and rendered detachably mountable on the main body of the image forming apparatus.
2. Related Background Art
The electrophotographic image forming apparatus (hereinafter referred to as an image forming apparatus) utilizing the electrophotographic image forming process achieves image recording by applying selective exposure to a uniformly charged image bearing member (photosensitive drum) to form a latent image thereon, developing such latent image with developer (toner) to form a visible image, transferring such visible image (toner image) onto a recording medium and fixing the transferred image onto the recording medium. The photosensitive drum after the image transfer is subjected, after the removable of remaining toner by cleaning means, to uniform charging by charging means and is used again in the image forming process starting from the exposure step.
In the image forming apparatus utilizing such electrophotographic image forming process, there is already adopted a process cartridge system in which an electrophotographic photosensitive member and process means acting on the electrophotographic photosensitive member are made integrally into a cartridge, which is detachably mountable on the main body of the image forming apparatus. Such process cartridge can significantly improve operability, since the maintenance of the apparatus can be achieved by the user instead of the serviceman. Such a process cartridge system is, therefore, widely employed in image forming apparatus.
Such process cartridge comprises a cleaning unit rotatably supporting the photosensitive drum and incorporating cleaning means and charging means, and a developing unit incorporating developing means and a toner container. The developing unit is provided with a developer bearing member (developing roller) of the developing means, supported rotatably with respect to the cleaning unit so as to be opposed in parallel to the photosensitive drum with a predetermined gap thereto, and a spacer for maintaining the predetermined gap between the developing roller and the photosensitive drum with a predetermined pressure in order to maintain the predetermined gap therebetween.
In order to obtain a satisfactory image in the image forming apparatus utilizing such process cartridge, it is required that the process cartridge is properly mounted in a predetermined position in the image forming apparatus and that the interfaces, such as electrical contacts and drive transmitting portions, are properly connected.
Consequently, there is being conceived and commercialized a configuration having positioning pins provided on the process cartridge on an axis of the photosensitive drum and a cartridge mounting and dismounting guide as guide grooves provided on the main body of the image forming apparatus for guiding and positioning the above-mentioned positioning pins, wherein the process cartridge is limited in rotation about the positioning pins by abutting against a fixed member in the main body of the image forming apparatus and a spring is provided on an openable and closable cover of the main body of the image forming apparatus for biasing the process cartridge, mounted in the main body of the apparatus, in the mounting direction.
There is also conceived a configuration having a back cover, matching an external shape of the process cartridge, on the internal face of the openable and closable cover, wherein the process cartridge is pushed into the proper position by the closing operation of the openable and closable cover.